Collaborative Research: Identification of the Plate Boundary Between India and Indochina Through Integrated Petrologic, Structural, and Paleomagnetic Analyses

0310306 Uddin PI建议进行综合的物源、构造和古地磁研究，以确定新生代早期印度东北角（阿萨姆邦/孟加拉国）和印度支那之间板块边界的位置。这一边界的精确位置将有助于印度和印度支那之间的接触（碰撞）年龄，这是目前知之甚少。始新世-渐新世（约1000年）的初步成分研究43至23 Ma）的前陆地层表明，存在两个截然不同的沉积序列。其中一个位于孟加拉盆地，其成熟沉积物来源于西部的印度克拉通。第二个，暴露在印度阿萨姆邦被解释为具有来自印度-缅甸山脉和/或喜马拉雅山脉最东端的造山源，作为印度支那的一部分，在东部和北部。这两个层序之间的边界没有暴露，但PI的假设是，它是在Kaladan断层附近，该断层具有年轻到活跃的位移。关于这两个层序，有两个可验证的假说与印度和亚洲之间碰撞的整个历史有关：（1）孟加拉盆地受到沉积物搬运障碍物的保护，如周边前隆;或者，（2）两个层序在前隆到达它们现在的位置之前被分开了相当长的距离。了解沉积时层序的古纬度对检验这些假设至关重要。如果这两个层序沉积在不同的板块上，那么孟加拉盆地可能已经向南延伸了约2500 km，在沉积的衰退阶段，它们之间的距离可能会减小。如果这些层序沉积在相似的纬度上，因此可能在同一个板块上，那么印度和印度支那之间的初始碰撞将发生在始新世/渐新世时期，而容纳印度向北运动的主要板块边界将在更远的东部。该项目的意义在于，在喜马拉雅东部前渊，这提供了一个机会，在一个约束良好的现代大陆碰撞，重建造山作用和表面过程，早于从西瓦利克和远孟加拉扇地层研究的土地上访问的基本上未开发的地层记录。孟加拉盆地和阿萨姆层序古纬度的澄清将为东南亚重建提供宝贵的信息。对卡拉丹断层两侧的前中新世层序进行详细的物源研究，包括砂岩岩石学、重矿物分析、矿物化学、单颗粒地质年代学和选定矿物相的同位素分析，将确定两个断层的沉积物来源，并与古地磁和构造研究相一致，将有助于重建早期第三纪碰撞的主要因素。拟议研究的更广泛影响：拟议研究将涉及在三个不同的机构培训三名研究生。学生们将相互合作，相互交流，PI将促进地质科学专业知识的发展。此外，至少有两名本科生将密切参与在奥本和新墨西哥州的研究方面。除了与美国几个学术机构（奥本、佛罗里达州、麻省理工学院、新墨西哥州）的科学家合作外，这项建议还涉及与得不到很好支持从事地球科学工作的国家（孟加拉国和印度）的地球科学家合作。PI计划尽可能及时地在具有广泛读者群的地球科学期刊上传播我们的工作成果。

0310306UddinThe PI's propose an integrated provenance, structural, and paleomagnetic study to determine the location of the plate boundary between the NE corner of India (in Assam/Bangladesh) and Indochina during early Cenozoic time. Precise location of this boundary will contribute to the age of contact (collision) between India and Indochina, which is presently very poorly known. Preliminary compositional studies on Eocene-Oligocene (ca. 43 to 23 Ma) foreland strata of the eastern Himalaya indicate that two dramatically different sedimentary sequences are present. One, exposed in the Bengal basin, has a mature sediment source from the Indian craton to the west. The second, exposed in Assam, India is interpreted to have an orogenic source from the Indo-Burman ranges and/or easternmost Himalayas, as part of Indochina, to the east and north. The boundary between these two sequences is not exposed, but the PI's hypothesize that it is near the Kaladan fault, which has young to active displacement. Two testable hypotheses regarding these two sequences bear on the overall history of collision between India and Asia: (1) the Bengal basin was protected from orogenic detritus by a barrier to sediment transport, such as a peripheral forebulge; or, (2) the two sequences were separated by a considerable distance before the terranes reached their present positions. Understanding the paleolatitudes of the sequences at the time of deposition is critical to testing these hypotheses. If the two sequences were deposited on different plates, the Bengal Basin could have been as far to the south as ~2500 km, with the distance between them probably decreasing during the waning stages of deposition. If the sequences were deposited at similar latitudes, and thus perhaps on the same plate, then the initial suturing between India and Indochina would have occurred during Eocene/Oligocene time and the major plate boundary that accommodated the northward movement of India would be farther to the east. The significance of this project lies in the largely unexploited stratigraphic record accessible on land in the eastern Himalayan foredeep, which provides the opportunity, in a well-constrained modern continental collision, to reconstruct orogenesis and surface processes that pre-date strata studied from the Siwaliks and the distal Bengal fan. Clarification of the paleolatitudes of the Bengal basin and Assam sequences will provide invaluable information for Southeast Asia reconstructions. Detailed provenance studies of the pre-Miocene sequences on both sides of the Kaladan fault, including sandstone petrology, heavy-mineral analysis, mineral chemistry, single- grain geochronology, and isotopic analyses of selected mineral phases, will define the sediment sources of the two terranes and, in concert with paleomagnetic and structural studies, will aid in reconstructing major elements of the early Tertiary collision.Broader impacts of the proposed research: The proposed research will involve the training of three graduate students at three separate institutions. The students will collaborate with one another and their interactions with each other and the PI's will foster the development of considerable breadth of expertise in the geological sciences. In addition, at least two undergraduate students will be intimately involved in aspects of the research at Auburn and New Mexico. In addition to collaboration with scientists from several academic institutions (Auburn, Florida State, MIT, New Mexico) in the United States, this proposal also involves collaboration with geoscientists from countries (Bangladesh and India) that are not well supported to do geoscience. The PI's plan to disseminate the results of our work in as timely a fashion as possible in geoscience journals with a broad readership.